DESCRIPTION: (Verbatim from application) This application proposes an intervention development study (IDS) to design a resistance exercise activity program that has the potential to preserve physical function and independence, is maximally accessible to older persons, is dose adjustable, and promotes maximal adherence. The IDS will use biomechanical investigation to identify those exercise activities and dosing levels that most effectively load the functionally important muscle groups of the lower extremity. Additionally, this application proposes the design of a randomized controlled intervention trial (RCT) to examine the efficacy, adherence, and side effects the activity program. The IDS will consist of a 3-phase, 40-week, single-armed, biomechanical examination of candidate exercises and resistance dosages in older adults (N=22; 70-85 years of age). In Phase I of the IDS (3 weekly data collection visits) we will use biomechanical tools (digital cameras, force platforms, and Newtonian physics) to differentiate the relative muscular loading associated with the performance of lower-extremity exercises that target the ankle plantarflexor, knee extensor, and hip extensor muscle groups. In Phase II of the IDS (1 data collection visit) we will again use biomechanical investigation to characterize the dose/response relations between resistance weight and muscular loading. Resistances of 0% body weight (BW), 5% BW, and 10% BW will be provided via a weighted vest. The ankle, knee, and hip joint moments of force (measures of muscular loading) are the primary outcome measures that will be used to rank the candidate exercises and resistances. Additionally, subjects will participate in debriefing interviews to determine the participant's fondness for and/or aversion to the exercises. The data collected in Phases I and II will be used in Phase Ill to design an activity intervention program for an intermediate-length RCT. If supported by the data in Phases I and II, during Phase III we will also write an RO1 proposal for the RCT.